A minimalist coding-agent harness
Tau is a terminal coding agent in Python — and a phase-by-phase reference for how one is actually built. Named for τ = 2π: one full turn, nothing hidden.
Models stream events. A thin layer turns provider responses into a single, ordered event stream you can follow line by line.
A portable brain: the loop that turns events into tool calls, owns transcript and session state, and stays free of any one app.
Files, shell, sessions, skills, commands, and a terminal UI — one concrete coding environment built on the harness.
The boundary
The τ harness is the agent. The session is its environment. The terminal is just one possible face. Keep them apart and the whole thing stays legible.
Every package has one job and can be explained without the others. No framework you have to believe in.
The control flow is on the page. Streaming, tool calls, sessions — readable top to bottom.
Each commit adds one understandable piece, so the repo doubles as a course in how agents are assembled.
It is a real terminal agent you can run today — the teaching is a side effect of the design, not a toy.
Start the loop. Watch a coding agent run with nothing hidden between you and the code.